The animal world is a world full of mystery and still to this day we are discovering new species of life all over this amazing planet. One place that’s the hardest to find is in the small kingdom, it’s easy to spot an animal as large as an elephant but when we zoom into the world bellow the planet becomes much larger and holds many more secrets waiting for us to find. Here is the top 5 smallest animals in the world.
#5 Copepod 1.2mm
Copepods (/ˈkoʊpɪpɒd/; meaning “oar-feet”) are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic (drifting in sea waters), some are benthic (living on the ocean floor), and some continental species may live in limnoterrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests, bogs, springs, ephemeral ponds, and puddles, damp moss, or water-filled recesses (phytotelmata) of plants such as bromeliads and pitcher plants. Many live underground in marine and freshwater caves, sinkholes, or stream beds. Copepods are sometimes used as biodiversity indicators.
As with other crustaceans, copepods have a larval form. For copepods, the eggs hatches into a naplius form, with a head and a tail but no true thorax or abdomen. The larva molts several times until it resembles the adult and then, after more molts, achieves adult development. The naplius form is so different from the adult form that it was once thought to be a separate species.
Copepods vary considerably, but can typically be 1 to 2 mm (0.04 to 0.08 in) long, with a teardrop-shaped body and large antennae. Although like other crustaceans, they have an armoured exoskeleton, they are so small that in most species, this thin armour, and the entire body, is almost totally transparent. Some polar copepods reach 1 cm (0.39 in). Most copepods have a single median compound eye, usually bright red and in the centre of the transparent head; subterranean species may be eyeless. Like other crustaceans, copepods possess two pairs of antennae; the first pair is often long and conspicuous.
#4 Spider Mite 1mm
Spider mites are members of the Acari (mite) family Tetranychidae, which includes about 1,200 species. They generally live on the undersides of leaves of plants, where they may spin protective silk webs, and they can cause damage by puncturing the plant cells to feed. Spider mites are known to feed on several hundred species of plants.
Spider mites are less than 1 millimetre (0.04 in) in size and vary in color. They lay small, spherical, initially transparent eggs and many species spin silk webbing to help protect the colony from predators; they get the “spider” part of their common name from this webbing.
#3 Crustacean 1mm
Crustaceans (Crustacea /krʌˈsteɪʃə/) form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill, woodlice and barnacles. Thanks to recent molecular studies, it is now well accepted that the crustacean group comprises all animals in the Pancrustacea clade other than hexapods. In other words, some crustaceans are more closely related to insects and other hexapods than they are to certain other crustaceans.
The 67,000 described species range in size from Stygotantulus stocki at 0.1 mm (0.004 in), to the Japanese spider crab with a leg span of up to 3.8 m (12.5 ft) and a mass of 20 kg (44 lb). Like other arthropods, crustaceans have an exoskeleton, which they moult to grow. They are distinguished from other groups of arthropods, such as insects, myriapods and chelicerates, by the possession of biramous (two-parted) limbs, and by their larval forms, such as the nauplius stage of branchiopods and copepods.
Most crustaceans are free-living aquatic animals, but some are terrestrial (e.g. woodlice), some are parasitic (e.g. Rhizocephala, fish lice, tongue worms) and some are sessile (e.g. barnacles). The group has an extensive fossil record, reaching back to the Cambrian, and includes living fossils such as Triops cancriformis, which has existed apparently unchanged since the Triassic period. More than 10 million tons of crustaceans are produced by fishery or farming for human consumption, the majority of it being shrimp and prawns. Krill and copepods are not as widely fished, but may be the animals with the greatest biomass on the planet, and form a vital part of the food chain. The scientific study of crustaceans is known as carcinology (alternatively, malacostracology, crustaceology or crustalogy), and a scientist who works in carcinology is a carcinologist.
#2 Tardigrade 0.5mm
Tardigrades (/ˈtɑːrdɪˌɡreɪd/; also known as water bears or moss piglets) are water-dwelling, eight-legged, segmented micro-animals. They were first discovered by the German zoologist Johann August Ephraim Goeze in 1773. The name Tardigrada (meaning “slow stepper”) was given three years later by the Italian biologist Lazzaro Spallanzani. They have been found everywhere from mountaintops to the deep sea, from tropical rain forests to the Antarctic.
Tardigrades are notable for being perhaps the most durable of known organisms: they can survive extreme conditions that would be rapidly fatal to nearly all other known life forms. They can withstand temperature ranges from 1 K (−458 °F; −272 °C) (close to absolute zero) to about 420 K (300 °F; 150 °C), pressures about six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human, and the vacuum of outer space. They can go without food or water for more than 30 years, drying out to the point where they are 3% or less water, only to rehydrate, forage, and reproduce.
They are not considered extremophilic because they are not adapted to exploit these conditions. This means that their chances of dying increase the longer they are exposed to the extreme environments, whereas true extremophiles thrive in a physically or geochemically extreme environment that would harm most other organisms.
Usually, tardigrades are about 0.5 mm (0.02 in) long when they are fully grown. They are short and plump with four pairs of legs, each with four to eight claws also known as “disks”. The first three pairs of legs are directed ventrolaterally and are the primary means of locomotion (moving), while the fourth pair is directed posteriorly on the terminal segment of the trunk and is used primarily for grasping the substrate. Tardigrades are prevalent in mosses and lichens and feed on plant cells, algae, and small invertebrates. When collected, they may be viewed under a very low-power microscope, making them accessible to students and amateur scientists.
Tardigrades form the phylum Tardigrada, part of the superphylum Ecdysozoa. It is an ancient group, with fossils dating from 530 million years ago, in the Cambrian period. About 1,150 species of tardigrades have been described. Tardigrades can be found throughout the world, from the Himalayas (above 6,000 m (20,000 ft)), to the deep sea (below 4,000 m (13,000 ft)) and from the polar regions to the equator.
#1 House Dust Mite 0.2mm
The house dust mite (HDM) is a cosmopolitan pyroglyphid that lives in human habitation. Dust mites feed on organic detritus, such as flakes of shed human skin, and flourish in the stable environment of dwellings. House dust mites are a common cause of asthma and allergic symptoms worldwide. The mite’s gut contains potent digestive enzymes (notably proteases) that persist in their feces and are major inducers of allergic reactions such as wheezing. The mite’s exoskeleton can also contribute to allergic reactions. The European house dust mite (Dermatophagoides pteronyssinus) and the American house dust mite (Dermatophagoides farinae) are two different species, but are not necessarily confined to Europe or North America; a third species Euroglyphus maynei also occurs widely. Unlike scabies mites or skin follicle mites, house dust mites do not burrow under the skin and are not parasitic.
House dust mites, due to their very small size and translucent bodies, are barely visible to the unaided eye. A typical house dust mite measures 0.2–0.3 millimetres (0.008–0.012 in) in length. For accurate identification, one needs at least 10× magnification. The body of the house dust mite has a striated cuticle.